The present invention concerns a portable object such as, in particular, a timepiece, including a piezoelectric transducer for entering data manually. More particularly, the object of the present invention is to use the piezoelectric transducer operating as a sound generator in a wristwatch with an alarm device to perform the function of a push-button switch.
There is known from U.S. Pat. No. 5,742,564 in the name of Junghans Uhren GmbH a timepiece such as a wristwatch including a flat or slightly dished case which is hermetically sealed by a crystal. A circular plate acting as a dial carries hour-symbols. This plate, arranged under the crystal, is fitted by force in the case. It is delimited at its periphery by a support collar which extends along the cylindrical inner surface of the case and which defines a space between the crystal and said plate in which the hands of the watch move. Piezoelectric sensors, preferably four in number, are arranged at regular intervals on the edge of the collar, between that edge and the edge facing the crystal. These sensors act as control switches for the horological functions of the watch. They are actuated manually by axial pressure on the edge of the crystal. In order to be able to respond to the stress exerted by the user, the crystal has to be able to move slightly. For this purpose, the crystal is mounted resiliently with respect to the case by means of a rigid rubber ring. The piezoelectric sensors are connected to an electric circuit arranged under the dial and which detects the pressure exerted on the sensors.
The invention disclosed in the Junghans Patent provides a wristwatch which has no stem or push-button and which is therefore less expensive to manufacture and has a more attractive aesthetic appearance. The horological functions of this watch are controlled by simple mechanical pressure on piezoelectric sensors which, in response to this stress, generate an electric voltage which acts on the desired horological function via an appropriate electronic circuit.
The Junghans watch unfortunately has certain drawbacks from among which one may cite the fact that the crystal has to be mounted so as to be able to move slightly, which poses significant problems for fitting this crystal with respect to the watch case. These problems of course have a negative effect on the manufacturing costs and are only partially resolved by the use of a rigid rubber ring arranged between said crystal and the middle part of said case. Indeed, because of its rigidity, it is difficult for the rubber ring to compensate for the plays between the crystal and the watch case, so that proper sealing cannot be guaranteed. There is thus a significant risk of humidity penetrating the watch which, as will easily be understood, is not acceptable. Likewise, particles of solid material can come between the rubber ring and the crystal and cause the operation of the mechanism to seize. Finally, as described above, the Junghans system is actuated by a succession of mechanical pressures exerted on the watch crystal. Under the effect of these pressures, the piezoelectric sensors are deformed and generate an electric voltage which is applied to the input of an electronic interpretation circuit. In response to this signal, the electronic circuit will act on the desired horological function. Repetition of such pressures is liable, after a certain time, to damage or even make the sensors unusable. Above all, it is not easy for the user to exert sufficient pressure to actuate the sensors without such pressure being excessive and liable to damage the sensors.
The object of the present invention is to overcome the above problems and drawbacks in addition to others by proposing a portable object whose manual data entry means include a piezoelectric transducer which is not liable to be damaged by excessive mechanical pressure.
The present invention therefore concerns a portable object such as, in particular, a timepiece, including means for displaying at least one data item and a case formed of a top portion including a crystal covering the display means and a bottom portion delimited by a back cover located below said display means, this object including a piezoelectric transducer generating an electric voltage when mechanical pressure is exerted on said top portion, the voltage generated by the piezoelectric transducer being applied to a first electronic circuit which will generate a logic signal in response to the pressure exerted, this electronic circuit being arranged inside said case, characterised in that said piezoelectric transducer is arranged in the bottom portion of said case and is rigidly connected to said case.
As a result of these features, the mechanical pressure which accompanies the manual entry of an item of data can be exerted at any location on the surface of the crystal. Under the effect of this pressure, the wrist of the person wearing the watch exerts a reaction force on the case. The latter is then very slightly deformed, whether it is made of plastic material, metal or another material. Since the piezoelectric transducer is rigidly connected to the case, it is deformed by the deformations of the case and generates, in a conventional manner, an electric voltage in response to this deformation. Thus there is no longer a risk of damaging the transducer by the effect of too high mechanical pressure. Likewise, the transducer, which is no longer wedged between a fixed part and a moving part, can bear a very high number of successive applications of pressure without its physical features deteriorating over time.
Another advantage of the present invention lies in the fact that the portable object does not include any moving parts. Thus, in the particular case of a timepiece such as a wristwatch, the watch crystal is fixedly mounted with respect to the case of said watch, for example by bonding or ultrasound welding or by driving it in while inserting a gasket between the crystal and the case. The sealing of the watch is thus not altered and the construction of such a watch proves very simple and thus inexpensive.
The present invention provides a watch whose horological functions can be controlled by applications of simple mechanical pressure on the crystal. Thus, the watch can do without a stem or push-button, which further reduces its manufacturing costs. Of course, other systems exist for entering data via tactile pressure which use, for example, capacitive, inductive, ultrasound or infrared keys. The drawback of such systems however lies in the fact that before being able to be used, they have to be placed in an active instruction receiving mode in which they use electric current. Conversely, the data entry system according to the present invention is permanently available without using any current.
According to a complementary feature of the invention, the portable object further includes a second electronic circuit which causes the piezoelectric transducer to operate as a vibration source for a sound generator.
As a result of this feature, the same piezoelectric transducer can be used both as a sound generator for an alarm device, for example in an electronic wristwatch, and as means for entering data by applications of mechanical pressure on the crystal of said watch. Such an embodiment, as will easily be understood, is particularly advantageous. It allows the number of components used to be reduced, and thus the volume which these components occupy in the case, and to limit the manufacturing costs.